1. Field of the Invention
The invention relates to hearing aids. The invention, more specifically, relates to hearing aids wherein part of the shell is custom made. The invention, in particular, relates to customized ITE (In-The-Ear) hearing aids. The invention further relates to methods of assembling a hearing aid.
2. The Prior Art
U.S. Pat. No. 5,487,012 explains the manufacturing of a shell for a hearing aid by computerized modelling of a shell adapted to the ear canal of a user and then building the shell by consecutive laser curing of layers of plastics. This method is traditionally referred to as digital shell manufacturing or Rapid Prototyping, although the method in the context of hearing aids is commonly used for manufacturing of the end product rather than prototypes.
When producing a custom shell for a hearing aid by a digital shell manufacturing method, it is difficult to obtain small tolerances. Therefore, it is common within the field to produce in a digital shell manufacturing process only the inner shell part, i.e. the part of the shell that should match the contours of the ear canal and the part of it that faces towards the eardrum, whereas the outer part, i.e. the part that faces the surroundings, or at least a section of that part, has been constituted by a faceplate manufactured by another method, e.g. injection molding. By producing the faceplate by injection molding it is possible to obtain a product with small tolerances and strong mechanical properties. However, separate manufacturing of the faceplate and the inner shell part complicates the manufacturing of the hearing aid, as the faceplate needs to be trimmed and joined to the inner shell part, e.g. by cutting and gluing.